834 



BOTANY AND PHARMACOGNOSY. 



Habit : Tabular on the macropinacoid, the crystal being 

 elongated on the c axis and terminated by the faces of the 

 brachydome (on j. The ratio of length to width is 2 : i or over, 

 the crystals often appearing rod-like and needle-like. The base 

 sometimes appears to the exclusion of the brachydome, giving 

 a s(|uare-ended crystal. The prism bevels the long edges of the 

 crystal at a very acute angle, which was only approximately 

 determined, hence the a: b ratio given above is largely in error. 



Fig. 332. Codeine: x-shaped skeleton crystals from lo per cent, alcoholic solution. 



X-shaped interpenetrating twins are observed, the angle between 

 the long dimensions of the two individuals being about 30. The 

 twinning law was not determined. 



Optical properties : The direction of greatest elongation of 

 the crystal (c) is the direction of less refractive index for the 

 aspect on the macropinacoid. No good interference figure was 

 obtained, although it is probable that the axial plane is the 

 brachypinacoid (010). If this is the case the orientation is 

 ei=c; 6=6; C=a. 



